In recent years, the use of mobile terminal apparatuses, such as cellular phones or PDAs (Personal Digital Assistances), has been spreading explosively, and there have been active movements to add a variety of functions to such mobile terminal apparatuses in order to expand their uses. Conventionally, voice communications were the main purpose for cellular phones, but today there are even types that allow the downloading of map information and displaying the present position on the map.
A mobile terminal apparatus, with a GPS (Global Positioning System) function built into it, can display on the screen a present position on map information downloaded. To increase the convenience of a mobile terminal apparatus, it is preferable that a navigation function to a destination be further realized. To accomplish it, it is necessary to provide thereon an azimuth sensor that measures the direction from present position to destination. Azimuthal information from the azimuth sensor, if it can be obtained, can complement the positional information based on GPS information, thereby enabling a screen display and voice guidance of the route to the destination.
A magnetic detection device is used for the measurement of azimuth. A magnetic detection device detects not only natural magnetic fields but also dynamic magnetic fields generated by the internal structure of the mobile terminal apparatus as well as by nearby electrical equipment or the like. Hence, in order to extract the natural magnetic field component only, it is necessary to delete the dynamic magnetic components from the magnetic components detected. When a two-axis magnetic detection device is used, the magnetic field strength cannot be determined, so that it is difficult to remove the dynamic magnetic components efficiently. Under these circumstances, consideration is now being given to the introduction of a three-axis magnetic detection device in order to determine the magnetic field strength.
In order to detect each of the three-axis components of terrestrial magnetism vector, it is necessary that a magnetic detection device be provided with at least three magnetic detection elements. In particular, since a mobile terminal apparatus is subject to spatial limitations, it is a mandatory requirement to employ a smaller size for a three-axis magnetic detection device when it is introduced into the mobile terminal apparatus.